Current News Archive

31 March 2020
Medical Health Physics Section: COVID-19 Information

Bryan Lemieux, MS, CHP, DABMP, Section President

In light of the current COVID-19 situation, you may soon find yourself being asked about the possibility of using linear accelerators or blood/research irradiators for "sterilizing" hospital personal protective equipment (PPE). One of the Medical Health Physics Section board members has recently pulled together the following information to address just this question. Our hope is that by sharing this information we can assist you in providing a quick and accurate response to your health care leaders.

Whether you can use irradiation for sterilization will entirely depend on dose rates available on your equipment; however, it is highly unlikely that you will have equipment at a hospital or affiliated research institution capable of efficiently delivering the required doses. Blood irradiators are used to deliver doses between 10–50 Gy for the prevention of graft-versus-host disease—these are not sterilization doses (IAEA 2008).

If you are looking to kill only coronavirus, we don't know the D10 dose yet for the strains causing the current pandemic. The D10 dose is defined as the dose that will result in a 90% reduction in virus. For example, we know that the D10 dose of 3.1 kGy has been measured for the transmissible gastroenteritis species of coronavirus genus of coronociridae family of viruses in cell culture medium (Australia Department of Agriculture 2014). Again, this is not the same species or media that we are talking about, but is useful to illustrate the core issue. You would need a minimum of 360 Gy min-1 capability to complete this in 10 minutes, which in this case may result in a 90% kill. It has been documented elsewhere that for a similar virus, SARS-CoV, a dose of 50 kGy was needed to reduce the infectivity in a tissue culture to nondetectable (Feldmann et. al).

If you are concerned about bacteria in addition to COVID-19, the European standard for sterilization of medical devices is 25 kGy. Now you would need to be capable of something on the order of 2,500 Gy min-1 to accomplish sterilization in 10 minutes.

Other considerations include the effect on the PPE materials under high-dose radiation exposure.

Key questions to ask if you are asked to look into this:

  • What are the maximum dose rates possible on your equipment?
  • Can the equipment be run for the time necessary to reach 25 to 50 kGy?
  • What is the expected absorbed dose to the virus on the PPE vs the dose to the virus in cell culture media or similar?

Consider reviewing IAEA's publication Trends in Radiation Sterilization of Health Care Products—Chapter 7 includes summaries of many of the key items to consider if you do decide to use radiation for sterilization purposes.

One board member has evaluated this possibility at their site for their available equipment and it would need to run continuously for 3 to 10 days. This is not an option.

Stay safe out there!

 

References

International Atomic Energy Agency. Trends in radiation sterilization of health care products. Vienna: International Atomic Energy Agency [online]. 2008. Available at https://www-pub.iaea.org/MTCD/publications/PDF/Pub1313_web.pdf. Accessed 30 March 2020.

Australia Department of Agriculture. Gamma irradiation as a treatment to address pathogens of animal biosecurity concern CC BY 3.0 [online]. Canberra: Australia Department of Agriculture. 2014. Available at https://www.agriculture.gov.au/sites/default/files/sitecollectiondocuments/ba/memos/2014/gamma-irradiation-review.pdf. Accessed 30 March 2020.

Feldmann F, Shupert WL, Haddock E, Twardoski B, Feldmann H. Gamma irradiation as an effective method for inactivation of emerging viral pathogens. Am J. Trop. Med. Hyg., 100(5):1275–1277; 2019. DOI:10.4269/ajtmh.18-0937.